A self-assembled, modular nucleic acid-based nanoscaffold for multivalent theranostic medicine.

Rationale: Within the field of personalized medicine there is an increasing focus on designing flexible, multifunctional drug delivery systems that combine high efficacy with minimal side effects, by tailoring treatment to the individual. Methods: We synthesized a chemically stabilized ~4 nm nucleic acid nanoscaffold, and characterized its assembly, stability and functional properties in vitro and in vivo. We tested its flexibility towards multifunctionalization by conjugating various biomolecules to the four modules of the system. The pharmacokinetics, targeting capability and bioimaging properties of the structure were investigated in mice. The role of avidity in targeted liver cell internalization was investigated by flow cytometry, confocal microscopy and in vivo by fluorescent scanning of the blood and organs of the animals. Results: We have developed a nanoscaffold that rapidly and with high efficiency can self-assemble four chemically conjugated functionalities into a stable, in vivo-applicable system with complete control of stoichiometry and site specificity. The circulation time of the nanoscaffold could be tuned by functionalization with various numbers of polyethylene glycol polymers or with albumin-binding fatty acids. Highly effective hepatocyte-specific internalization was achieved with increasing valencies of tri-antennary galactosamine (triGalNAc) in vitro and in vivo. Conclusion: With its facile functionalization, stoichiometric control, small size and high serum- and thermostability, the nanoscaffold presented here constitutes a novel and flexible platform technology for theranostics.

Oligolysine-based coating protects DNA nanostructures from low-salt denaturation and nuclease degradation.

DNA nanostructures have evoked great interest as potential therapeutics and diagnostics due to ease and robustness of programming their shapes, site-specific functionalizations and responsive behaviours. However, their utility in biological fluids can be compromised through denaturation induced by physiological salt concentrations and degradation mediated by nucleases. Here we demonstrate that DNA nanostructures coated by oligolysines to 0.5:1 N:P (ratio of nitrogen in lysine to phosphorus in DNA), are stable in low salt and up to tenfold more resistant to DNase I digestion than when uncoated. Higher N:P ratios can lead to aggregation, but this can be circumvented by coating instead with an oligolysine-PEG copolymer, enabling up to a 1,000-fold protection against digestion by serum nucleases. Oligolysine-PEG-stabilized DNA nanostructures survive uptake into endosomal compartments and, in a mouse model, exhibit a modest increase in pharmacokinetic bioavailability. Thus, oligolysine-PEG is a one-step, structure-independent approach that provides low-cost and effective protection of DNA nanostructures for in vivo applications.

Quantification of cellular uptake of DNA nanostructures by qPCR.

DNA nanostructures facilitating drug delivery are likely soon to be realized. In the past few decades programmed self-assembly of DNA building blocks have successfully been employed to construct sophisticated nanoscale objects. By conjugating functionalities to DNA, other molecules such as peptides, proteins and polymers can be precisely positioned on DNA nanostructures. This exceptional ability to produce modular nanoscale devices with tunable and controlled behavior has initiated an interest in employing DNA nanostructures for drug delivery. However, to obtain this the relationship between cellular interactions and structural and functional features of the DNA delivery device must be thoroughly investigated. Here, we present a rapid and robust method for the precise quantification of the component materials of DNA origami structures capable of entering cells in vitro. The quantification is performed by quantitative polymerase chain reaction, allowing a linear dynamic range of detection of five orders of magnitude. We demonstrate the use of this method for high-throughput screening, which could prove efficient to identify key features of DNA nanostructures enabling cell penetration. The method described here is suitable for quantification of in vitro uptake studies but should easily be extended to quantify DNA nanostructures in blood or tissue samples.